Investigators are focusing on train warnings

Tim Fischer/Associated Press

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Johnie Lee Qualls, left, comforts and talks with Terry Johnson, Friday, Nov. 16, 2012, in Midland, Texas, before a community prayer service to pray for all those involved in an incident Thursday, where four veterans were killed and 16 other people were injured when a train slammed into a parade float carrying the returning heroes to a banquet. (AP Photo/Reporter-Telegram, Tim Fischer)

Johnie Lee Qualls, left, comforts and talks with Terry Johnson, Friday, Nov. 16, 2012, in Midland, Texas, before a community prayer service to pray for all those involved in an incident Thursday, where four veterans were killed and 16 other people were injured when a train slammed into a parade float carrying the returning heroes to a banquet. (AP Photo/Reporter-Telegram, Tim Fischer)